Timing of growth determines fitness and performance of a galling insect on willow

Abstract

Characteristics that determine a plant's quality as herbivore food exhibit within‐plant heterogeneity. Most models suggest negative effects from secondary chemicals. Less work has focused on plant growth dynamics that might also be important in creating heterogeneity in the distribution of food resources among leaves within the plant. Gall‐forming insects are sessile during their feeding stage and are therefore of particular interest when assessing the relative importance of growth and non‐growth processes in plants. Galls act as sinks for photoassimilates, and successful redirection of these resources requires that gall formation takes place in plant modules that are in an active growth phase. The gall midge Dasineura marginemtorquens infests leaves of the fast‐growing Salix viminalis. Several young leaves per shoot are used as oviposition sites during any single egg‐laying occasion. This study investigates the extent to which growth in leaves that are apparently suitable for gall initiation varies along shoots of S. viminalis, and tests whether or not such variation affects the fitness and performance of D. marginemtorquens. The relative position of the galled leaves along a shoot was found to determine the success of the gall midge in terms of larval survival, larval developmental time, and adult size. Leaf growth dynamics, but not leaf size, was associated with the variation in insect fitness and performance. Thus, when considering habitat quality for a sessile insect like D. marginemtorquens, the length of time that the galling site acts as a photoassimilate sink is more important than the final size of the plant module.

Plant phenological asynchrony and community structure of gall‐inducing insects associated with a tropical tree species

“…Because gall‐inducing insect species have the ability to manipulate the growth and development of plant tissues (Cuevas‐Reyes, Quesada, Siebe, & Oyama, ; Cuevas‐Reyes, Siebe, Martínez‐Ramos, & Oyama, ) and may also be capable of modifying host nutritional quality and plant secondary metabolites for protection against natural enemies (Pascual‐Alvarado, Cuevas‐Reyes, Quesada, & Oyama, ), this insect guild tends to be less affected by quality of host plant tissues (Höglund, ). Therefore, adult females must select the most adequate sites for oviposition for their offspring to reach higher success (Cuevas‐Reyes, Quesada, Hanson, Dirzo, & Oyama, ).…”

“…Second, the galls are sessile and their formation is associated with an alteration in plant resource allocation, which occurs a few hours after oviposition (Höglund, 2014), with possible effects on the oviposition site selection by females of other galling insects (Cornelissen, Guimarães, Viana, & Silva, 2013). Third, the success of the gall-inducing insect also depends on the selection of the most vigorous organ of the plant (resource quality) and the number of oviposition sites (resource abundance) available for its development (Höglund, 2014;Price, 1991). Moreover, the performance of gall-inducing insects is also affected by the interaction between plant phenology and top-down forces (Fagundes et al, 2005;Hood & Ott, 2010;Johansson et al, 2015) as well as by biological interactions that occur within the same trophic levels (Cornelissen et al, 2013;Johansson et al, 2015).…”

Adaptation to different host plant ages facilitates insect divergence without a host shift

“…To the best of our knowledge, this is the first study to document divergent selection associated with host plant age, a process that has the potential to be quite common especially among insects that feed on long-lived plants. Particularly for sessile, gall-inducing insects, the age of host plant tissue can significantly impact insect fitness [54][55][56]. Ontogenetic changes in plant defence have been well characterized [57], and age-specific differences in defensive chemistry, physical defence traits or nutrient content [58][59][60] could restrict the feeding patterns of phytophagous insects and/or require specialized adaptations.…”

Variation in community structure of gall‐inducing insects associated with a tropical plant supports the hypothesis of competition in stressful habitats

“…For example, gall‐inducing insects have high specificity with regard to their host plant and the target organ to oviposition (Carneiro et al, ; Joy & Crespi, ) they synchronize the oviposition period with the plant phenological period, where there is growth but the tissues are not yet lignified (Whitham, ; Yukawa, ). Soon after oviposition, hatched larvae of galling insects induce rapid morphological and physiological changes in host plant tissue, draining resources for their own development (Höglund, ; Ollerstam, Rohfritsch, Höglund, & Larsson, ), which potentially interferes with the oviposition behavior of females of other gall‐inducing insects species (Cornelissen et al, ). Because they are sessile and highly specific, galls are excellent models for understanding the effects of interspecific competition on community structuring (Cornelissen et al, ; Fagundes et al, ).…”